Field of the Disclosure
The present disclosure is directed to compositions comprising oil-in-water dispersions that include an oil phase composed of discrete oil particles coated with a solid material and dispersed in an aqueous phase; and each oil particle contains one or both of an organic ultraviolet A (UVA) absorbing compound or an organic ultraviolet B (UVB) absorbing compound.
Description of Related Technology
Sunscreen is a vital tool that can help prevent UV radiation-induced cancer and skin photoaging. Commercially available sunscreen compositions, however, often exhibit less than optimal in vivo SPF efficiency and photo stability. For example, the average in vivo efficiency of sunscreen compositions is about 1.6 SPF units per 1 wt. % sunscreen composition, based on the total weight of the composition (for SPF 15 and 30), with best-in-class metal oxide-based and organic-based sunscreen formulations exhibiting in vivo efficiencies of only about 6 and 4 SPF units, respectively, per 1 wt. % sunscreen composition. Further, broad-spectrum sunscreen compositions are highly recommended because they protect against both UVA and UVB irradiation. However, these compositions are inherently photounstable due to the interaction of the UVA and UVB absorbers with each other, and often require the inclusion of a photostabilizer. Because of the inefficiency and photoinstability of traditional sunscreen formulations, even when they include a photostabilizer, UV absorbers must often be present in the formulations in relatively high concentrations to produce an adequate effect. For example, sunscreens having SPF values of 15 or 30 often require about 10 wt. % to 20 wt. % of UV active compounds, respectively, based on the total weight of the sunscreen composition. Including such a high concentration of UV absorbers in a sunscreen formulation, however, can be problematic because of the tendency of the absorbers to penetrate into a user's skin where they can interact with living tissues and/or migrate across skin, reducing SPF over time, and cause eye stinging.
Sunscreen manufacturers have attempted to improve the in vivo SPF efficiency and photostability of broad range sunscreen compositions by separating the UVA and UVB absorbers from each other, thereby preventing interactions that destabilize the UVA absorbers.
Some manufacturers have encapsulated organic UVA and UVB absorbers into solid lipid nanoparticles (“SLNs”). SLNs are generally spherical particles with average diameters between 50 and 500 μm that include a lipophilic core stabilized by surfactants, such as polyamide-3 (e.g., OLEOCRAFT technology by Croda, present in SYLVACLEAR and UNICLEAR sunscreens). See, e.g., U.S. Pat. Nos. 7,914,772; 7,892,524; and 8,524,203 and U.S. Patent Application Publication Nos. 2015/118273 and 2007/0086962 (to Unilever); U.S. Pat. Nos. 6,436,376 and 8,652,449 and U.S. Patent Application Publication No. 2006/0292095 (to L'Oreal); and U.S. Patent Application Publication No. 2003/0235540 (to Bernd Herzog), each incorporated by reference in its entirety. See also, Popa, et al., Co-Encapsulation of a mixture of Antioxidant and Sunscreen Agents Into Solid Lipid Nanoparticles, U.P.B. Sci. Bull., Series B, 76(2):45-56 (2014), which describes the co-encapsulation of an organic sunscreen material (octocrylene) and an antioxidant (Luteolin) together into SLNs. Although sunscreen compositions containing UV absorbers encapsulated in SLNs exhibit improved photostability, they display poor in vivo SPF efficiency (e.g., 2.3 SPF units per 1 wt. % sunscreen composition). Further, SLNs often require the use of high wax levels, which has a negative effect on skin feel and consumer acceptance. Further still, in many commercial formulations, the UVA and UVB absorbers are often present in the same oil phase, allowing them to interact with, and destabilize, each other.
Other manufacturers have encapsulated UV absorbers using plant-based materials. For example, Botaneco has separately encapsulated organic UVA and UVB absorbers in oleosomes using its HYDRESIA technology. The oleosomes include a center core of plant oils and vitamin E surrounded by a phospholipid membrane, and are stabilized by the protein oleosin. Over time, however, these oleosomes release the UV absorbers inside by collapsing on the skin, allowing the UVA and UVB absorbers to interact with and destabilize each other, and also allowing the absorbers to penetrate the skin.
Sol-Gel Technologies describes separately encapsulated UVA and UVB absorbers in silica glass (see e.g., U.S. Pat. No. 6,436,375, incorporated herein by reference in its entirety), licensed to Merck as the EUSOLEX UV-PEARLS technology. The silica glass encapsulation prevents the UVA and UVB absorbers from interacting with each other, which photostabilizes them. However, sunscreen compositions containing these microparticles exhibit only mediocre in vivo SPF efficiency, such as 0.9 to 1.8 SPF units per 1 wt. % sunscreen composition.
Other manufacturers have attempted to separately encapsulate UVA and UVB absorbers using various different technologies. Although the sunscreen compositions containing these separately encapsulated UVA and UVB absorbers can exhibit improved photostability, they all display poor or mediocre in vivo SPF efficiency. For example, Capsulent Technology has encapsulated oxybenzone by precipitating a cationic surfactant with a soluble anionic polymer to form Lewis acid-Lewis base salt walls. See U.S. Pat. No. 8,685,425 to Tycho Speaker, which is incorporated herein by reference in its entirety. However, these capsules easily break when applied to the skin. Id. at paragraph [0035]. Tagra Biotechnology has encapsulated organic and inorganic UV filters in unbreakable, transparent microcapsules using its SUNCAPS technology (see PCT Publication No. 2014/132261). However, sunscreen compositions containing UV absorbers enclosed in SUNCAPS displays an in vivo SPF efficiency of only about 2.7 SPF units per 1% sunscreen composition. Sunsmart has provided sunscreen-encapsulated particles formed from a matrix composed of a wax or polymer (e.g., oils, lipids, protein derivatives, alkylated vinylpyrrolidone polymers, long chain alcohols, long chain fatty acids, ethylene-acrylic acid copolymers, and ethylene-vinyl acetate copolymers). See, e.g., U.S. Pat. No. 5,733,531, which is incorporated herein by reference in its entirety. However, sunscreen formulations containing these particles also exhibit poor SPF efficiency. For example, the in vivo SPF efficiency for 5% octinoxate is 3.3 SPF units per 1% sunscreen composition. These capsules also require a high wax level, resulting in poor consumer acceptance. Other sunscreen formulations containing encapsulated UVA and UVB absorbers are described in International Patent Application Publication Nos. 2007/075747 (to Schering Plough Healthcare) and 2014/135360 (to Unilever), each incorporated herein by reference in its entirety.
Sunscreen manufacturers also have attempted to improve the photostability of broad range sunscreen compositions by encapsulating UVA and UVB absorbers in Pickering emulsions, which are emulsions that are stabilized by solid particles. See, e.g., U.S. Patent Application Nos. 2014/0134255 (to Shiseido) and 2014/0341981 and 2014/0341954 (to L'Oreal) and U.S. Pat. No. 5,500,223 (to Unilever), each incorporated herein by reference in its entirety. The known sunscreen compositions containing Pickering emulsions, however, also display poor in vivo SPF efficiency. Beiersdorf also describes sunscreen compositions containing UV active materials in Pickering emulsions. See, e.g., U.S. Pat. Nos. 6,379,680; 6,391,321; 6,410,035; 6,428,796; 6,440,399; 6,558,683; 6,579,529; 6,582,707; 6,592,883; 6,692,755; 6,767,547; 6,083,048; 6,838,088; 6,881,415; 7,037,511; and 7,186,415; U.S. Patent Application Publication No. 2005/0266055; and EP Patent No. 1627668, each incorporated herein by reference in its entirety. The Beiersdorf materials, however, also display poor in vivo SPF efficiency. Further, many of the sunscreen formulations that contain Pickering emulsion include the UVA and UVB absorbers in the same oil phase, allowing them to interact with, and destabilize, each other.
Although sunscreen manufacturers have made great strides in developing sunscreen compositions having improved photo stability, the improved photostability has not resulted in compositions that also have high in vivo SPF efficiency. Therefore, there is a need for sunscreen compositions that exhibit excellent photostability and high in vivo SPF efficiency, which would allow a lower concentration of UV absorbers to be present in the compositions, and also that limit or prevent the penetration of UV absorbers into a user's skin.